* { 
    margin: 0; 
    padding: 0; 
    box-sizing: border-box; 
}
html,body{
    width: 100%;
    height: 100%;
}
body {  
    width: 100%;
    height: 100%;
    background: url(../image/bg3.jpg);
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
    position: relative;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
} 